Transceiver circuit arrangement



July 26, 1949. D. J, BRAAK 2,477,039

TRANS CEIVER CIRCUIT ARRANGEMENT Filed Feb. 7, 1947 a I g 2g 7 Rccuvc -19.T

. INVENTOR. 1 DIRK IOHAN BRAAK AGENT Patented July 26, 1949 2,477,039 TRANSGEIVERCIRCUIT ARRANGEMENT fink Johan Bra 1;, :Eiiii lhoven, Netherlands, an signer to Hartford National Bithkaiid Trust Company, Hartrcra, 001111., as t'fli's't'e Application I ieb 'uary '7, 19.47 Serial 7%,9151 In the Netherlands January 5, 1944 Section 1, Public Law 690, August a, 1946 Patent expires January 5, 1964 9 claims.

It has already been proposed to simplify the control of a transceiver circuit arrangement; in which the carrier-wave frequency of the transmitter must correspond with the tuning frequency of the receiver, by making the transmitting frequency and the tuning of the receiver correspond automatically with one another by means of a control circuit, which is preferably connected to the receiver and, provided that the transmitting frequency lies within control range determined by the construction of the control circuit, yields a positive or negative control: voltage according as to Whether the transmitting frequency is higher or lower than the tuning frequency of the receiver.

The control voltage derived from the: said control circuit, hereinafter the usual term ire'quencydiscriminator will be used, controls this case a reactance tube or other control member coupled with the frequency-determining circuit oi the transmitter, for example in view of trequencymodulation of thecarrier waveto-be transmitted, in such a manner that deviations of the transmitting frequency relatively to the tuning. of the receiver are substantially completely made up for.-

We have found that during operation. of transceiver circuit-arrangements of the aforesaid: kind it occurs, however, that theautomatic coupling of the transmitting frequency and thetuning. of the receiver by means of thefrequency discrimi-- nator falls out in spite of the fact that thetransmitting frequency proves to be steadily and amply within the controlrange of the frequency discriminator.

According to the inventionthe said. drawback of transceiver circuits of this kind is obviated by temporarily varying the transmitting. frequency occurring immediately upon changing over from reception to transmission relativelf to the tuning of the receiver.

The" invention is based.- on the recognition that the said drawback ensues-from the properties; of the discriminator inconjunction-- with the. switching-ofr of the transmitter during listening to a counterstation, as is necessary withtrarisceivers bod'i'ment of'the-invention,

Fig 2 is a schematic diagram of one preferred embodiment of the invention; and v Fig. 3' is aschematic diagram or another preferred; embodiment of the invention.- y in Fig. thetuning frequency (ordinate) of, for example; the frequency-determining circuit; of a transmitter is represented-as a functitm ofthe tuning capacity of the circuit; a discriminator bringing the tuning trequ'ency of the circuit; as much as possible into an agreement with the tuningirequency we given by, the discriminator. Now if thetuningcapacity is varied between two values, for example,- of from C1, to Q6, lying on either side of the value of Co of the tuning capacity corresponding. to thefrequency o, the relation betweenthe tuning frequency of the cireuitand the tuning capacity can, in principle; be represented by the curve I, 2, 3, 3, 4, 5,5 6.: At the points I, 2 the coupling to bebrought about by the discriminatorgis not yet operative. Qnly at a capacity value 633 slightl deviatin from C0 it'bec'oines operative; as a result oi which the f r equeney ws'jsreadjusted to the value ofwe? which differs only slightly from wo. Upon a; further I variation (C4) of the tuning capacity the coupling remains operative up toa capaci-ty value Ce materially deviating from C0-,- when it fallsout, the tuning frequency than beginning: to: deviate considerably from we onaccount oii a variation leaping from 005 to m5, and the coupling f-urther (Cs) remaininginoperative Now ifthe: tuning capacity. is varied inversely, ire. from Cr were, the: curve 1,: 8;. 9; 93M, It; M, It is obtained in an analogous mariner as -explai-ned before.

I .At C9: the coupling becomes opera-121%,. at 611 inoperative. The range between and C11 is'reierreda-to as the control range or the discriminator, the much smaller range betw'een Csand G9 on the contrary astherangeof interference of the discriminator. Norma/l ly the interference range covers only a fraction of thecornir-oira'nge,-- regardless of the fact whether, for example; a disc'riminator of the: so-call'e'dphase-discriminating kind or watch type? is used, thisi raction being smaller as the control obtained becomes better (for example by using a=higher amplification of the" control-voltage:obtained) Now it atag'iven momentthe transmitter of the'arrangement is-us'ed and the transmittingfrequencyr is coupled: with: the" tuning frequency, of

the receiver by the discriminator, and 'af ter the transmitter has been cut out for some-time'wi-th avi'ew' to; listening to a'ccunter station; the transmittinga frequency and the tuning or the receiver,

- amplification stage II. r I

The receiving part arranged for superheteropled by the discriminator to render coupling inoperative, for it becomes operative only when the transmitting frequency is within the narrow interference range of the discriminator.

1' 1 Now by temporarily varying, according to the invention, either the transmitting frequency or the tuning frequency of thereceiver and/or of the discriminator after changing over from reception to transmission, thus bringing'the transmitting frequency into the interference range of the discriminator, the coupling between the transmitting frequency and the tuning frequency of the receiver becomes operative and will remain so even after the said temporary variation, provided only that the transmitting frequency was initially within the control range of the discriminator.

The temporary variations which has to bring the transmitting frequency for amoment within the interference range of the discriminator may,

inaccordance with time, exhibit inter alia the form of an aperiodic impulse, a damped oscilladenser, which is provided with a flexibly suspended electrode, in parallel with the frequencydetermining circuit of the transmitter, this condenser receiving an impetus when changing over from reception to transmission.

A construction of this kind may, however, also become operative by mechanical shocks or vibrations which, of course, is undesirable. It is there- 'fore advisable that the means procuring the required frequency variations should as much as possible be electrical.

It is eflicient and simple to make the device for changing over from reception to transmission directly bring about the desired voltage variation.

This again may be effected in various ways. In order that the invention may be clearly understood and readily carried into effect, it will now be explained more fully with reference to the accompanying drawing, given by way of example, in which Figures 2 and 3 illustrate forms of construction of a device according to the inventionpertaining to the last-mentioned category of constructions.

In the transceiver circuit arrangement shown in Fig. 2 the transmitting part is shown on the left, the receiving part on the right of an aerial The transmitting part comprises an oscillator I4 having a frequency-determining circuit l5 with which a reactance tube I6 is coupled. The oscillations generated and, as the case may be, modulated in frequency by the reactance'tube iii, are supplied to the aerial l3 through a power dyne reception comprises a high-frequency preamplification stage l8, a mixing stage IS, a local oscillator 20, an intermediate-frequency amplifier 2|, a detector 22 and a low-frequency amplifier 23 to which .a loudspeaker 24 is connected.

Accordingas to whether the device represent- 7 ed will be used for transmission or reception the transmitting or receiving part is connected to the aerial [3 by means of a transceiver switch 25. During reception the transmitter is switched 011", whereas during transmission the receiver re- "mains switched on, as the case may be with reduced sensitiveness, in view of bringing the transmitting frequency and the tuning of the receiver in agreement with one another, which takes place as follows.

During transmission (switch 25 turned to the left) the transmitted oscillations are also supplied to the receiver through a coupling condenser 26 having a low value. The oscillations picked up by the receiver control a frequency-discriminator 21 connected to the intermediate-frequency receiving part (2|); this discriminator produces apositive or anegative control-voltage at an output resistance 28 if the frequency of the incoming oscillations is higher or lower than the tuning frequency of the receiver. The control voltage obtained from the discriminator is introduced with such a polarity intothe control grid circuit30 of the reactance tube l6 of the transmitter connected to a negative bias battery 29 that deviations. of the transmitting frequency relatively to the tuning of the receiver are reduced.

In order to render the coupling between transmitting frequency and tuning of the receiver operative according to the invention when switching over fromreception to transmission the transceiver switch 25 has coupled to it a switch 3| which completes the charging circuit of a condenser 32 when switching over from reception to transmission. This charging circuit comprises, besides the switch 3|, successively a battery 33, the condenser 32 shunted by a leaksion. By a suitable choice of the amplitude of the impulses occurring in the control grid circuit 30 it is achieved that, regardless of the value of thetransmitting frequency lying within the control range and outside the interference range of the discriminator, the transmitting frequency, due. to theimpulses, has for a short time a frequency lying within the interference range, as a result of which the coupling between the trans- .mitting' frequency and the tuning of the receiver is brought about. V

A similar effect is obtainable by shuntingthe secondary winding. of the transformer 35 bya condenser. 36. The resonant circuit thus ensued in the control-grid circuit 30 receivesan impetus when closing the switch 3| and produces the appearance of a damped oscillation in the control gridcircuit, which causes a corresponding varia tion ,of the transmitting. frequency.

V In both cases set out in detail itgis of no im- 'portance in what direction the transmitting frequency varied with respect to the tuning of the receiver.

If only a unilateral variation of the transmitting frequency need be taken into account, the form of construction shown may be simplified by includingin the grid lead 30 a coil instead of the variation of the transmitting frequency to be anticipated.

Finally Fig. 3 shows one form of construction of an auxiliary circuit arrangement for the production of two succeeding voltage impulses having an opposite polarity, in which no inductive switching elements, but exclusively resistances and condensers are used.

The auxiliary circuit shown in Fig. 3 is arranged to cooperate with elements I3 to 28 and 30 in Fig. 2, the grid lead 30 for reactance tube I6 being connected serially through discriminator output resistor 28 and through the auxiliary circuit to ground.

The auxiliary circuit shown in Fig. 3 comprises two switches 38 and 39 which; are coupled with the transceiver switch 25 and, during reception, are turned downwards. Thus a condenser 40 connected between the grid lead 30 of the reactance tube i6 and earth has supplied to it through resistances M, 42 and the switch 39 by means of a battery 43, 44,9, voltage which is higher, for example two times as high (2 Vg), as the grid bias (Vy) required by the reactance tube I6. At the same time an auxiliary condenser 45 unilaterally earthed by the switch 38 is connected to the battery 43, 44 through the switch 39 and is thus also charged to a voltage of 2 V9.

On changing over to transmission the switches 38, 39 are turned upwards and the circuit-arrangement shown in Fig. 3 ensues, in which the normal grid bias (Vg) issupplied by the battery 43 to the condenser 40 through resistance 4|, switch 38, condenser with leakage resistance 42 and switch 39.

When operating the switches 38 and 39 the condenser 45 exhibits a charging voltage of 2 Vg which becomes operative in the last-mentioned circuit with a polarity opposite to that of the charging voltage of the condenser 40 and of the voltage of the battery 43. Immediately upon changing over from reception to transmission the junction between the resistances 4|, 42 will have a potential +2 Vg-Vg==+Vg relatively to earth.

By a suitable choice of the time constant of the discharging circuit of the condenser 45 it can now be achieved that the voltage of the condenser 40, initially being --2 V9, assumes a value between Vg and 0 or even a positive value shortly after changing over from reception to transmission, Whereas the final voltage set up at the condenser 40, after changing over from reception to transmission, will be Vg.

Thus it is achieved, as has been aimed at, that upon changing over from reception to transmission the grid of the reactance tube temporarily receives successively a higher and a lower bias than the required bias, so that the coupling between receiving and-transmittingfrequency can steadily become operative What I:claim is: a a

1. In combination with a transceiver including a transmitter provided with a. tuned circuit for determiningthe operating frequency thereof, a tunable receiver and means to switch-over from reception to transmission, apparatusfor automatically aligning the operating frequency of the transmitter with the frequency to which the receiver is tuned comprising a frequency control transceiver to apply momentarily an auxiliary control voltage to said device to swing the frequency of the transmitter into the operating range of said discriminator.

2. In combination with a transceiver including a transmitter provided with a tuned circuit for determining the operating frequency thereof, a tunable receiver and means to switch-over from reception to transmission, apparatus for automatically-aligning the operatin frequency of the transmitter with the frequency to-which the receiver is tuned comprising an electronic frequency control device coupled to the tuned circuit of said transmitter and arranged to adjust the frequency thereof in accordance with a control voltage, a frequency discriminator coupled to said receiver to develop a control voltage whose value is proportional to the deviation of the transmitter frequency relative to the frequency of the receiver within a predetermined range of deviation, means to apply said control voltage to said device to effect a corresponding adjustment in the'frequency of said transmitter, and means responsive to the switch-over operation in the transceiver to apply momentarily an auxiliary control voltage to said device to swing the frequency of said transmitter into said range of deviation.

3. A transceiver circuit as set forth in claim 2 wherein said auxiliary control voltage has the form of an aperiodic impulse,

4. A transceiver circuit as set forth in claim 2 wherein said auxiliary control voltage has the form of a damped oscillation.

5. A transceiver circuit as set forth in claim 2 wherein said auxiliary control voltage has the form of an undamped oscillation maintained for a predetermined period.

6. In combination with a transceiver including a transmitter provided with a tuned circuit for determining the operating frequency thereof, a tunable receiver and means to switch-over from reception to transmission, apparatus for automatically aligning the operating frequency of the transmitter with the frequency to which the receiver is tuned comprising a grid-controlled reactance tube coupled to the tuned circuit of said. transmitter and arranged to adjust the frequency thereof in accordance with a control voltage applied to the grid of said tube, means to apply a bias voltage to the grid of said tube, a frequency discriminator coupled to said receiver to develop a control voltage whose value is proportional to the'deviatio'n or" the transmitter frequency relative to the frequency of the receiver Within a predetermined range of deviatiommeans to apply said control voltage to the gridof said tube to effect a correspondingadjustment in the ire- Y quency of said transmitter, and means responsive to the switch-over operation in said transceiver for varying momentarily the bias on the grid of said tube to swing the frequency of said transmitter into said range of deviation,

7. In combination with atransceiver includ- 7 ing a transmitter provided with a tuned circuit for determining the operating frequency thereof, a tunable receiver and means to switch-over from reception to transmission, apparatus for automatically aligningthe operating frequency of the transmitter. withthe frequency to which the receiver is tuned comprising agrid-controlled reactance tube coupled to the tuned circuitl of said transmitter and arranged to adjust the frequency thereof in accordance ,witha control voltage applied to the grid of said tube, means to apply a bias voltage to the grid of said tube, a frequency discriminator coupled to said receiver to develop a control voltage whose'value is pro-- portional to the deviation of the transmitter frequency relative to the frequency of the receiver within a predetermined range of deviation, means to apply said control voltage to'the grid of said tube to eifect a corresponding adjust-v ment in the frequency ,of said transmitter, and means responsive to theswitch-over operation in said transceiverfor varying momentarily the bias on the grid of said tube, to swing the frequency of said transmitter into said range of deviation, said last named means including a capacitor, a source of charging voltage forsaid capacitor, a resistor connected across said capacitor, a transformer having a primary; and a secondary, a switch, said capacitor, said source, said primary and said switch being serially connected in a closedcircuit and means closing said whereby said capacitor is charged to develop a voltage impulse in saidsecondary, said voltage impulse being applied to vary the bias on the grid of said tube. v l

8. An arrangement, as set forth in claim 7,

determining the operatingfrequency thereof}; a tuned, receiver and means .to'switch-over'from reception to transmission, apparatus ,forautomatically aligningjthe operating frequency of the '/transmitter withthe frequency to which the receiver istuned comprising a grid-controlled reactance tube'coupled to the tuned circuitof said transmitter andarranged to adjust the frequency 'thereof in accordance with acontrol voltage applied to the grid of ,said tube, a frequency discriminator coupled to said receiver to develop a control voltage whose value is proportional to the switch upon the switch-over of said transceiver further including a capacitance connected across said secondary to define a resonant circuit.

deviation, of the transmitter frequency from the frequency of the receiver within a predetermined range of deviation, means tolapply said control voltage to the gridof said tube to effect a corresponding adjustment in the frequency of said transmitter, and means responsive to the switchover operation ,in said transceiver for varying 1 momentarily the bias on the grid of said tube to swing the frequency of said transmitter into said range of deviation, said last named means including afirst capacitor, asource of bias voltage, connected to said grid, a resistance, a second capacitor, a leakage resistor shunting said second capacitor, means for charging prior'to the switch over operation said first and second capacitors in oppositepolarity to a voltage which is higher than the voltage of said bias source, and means responsive to the switch-over operation for connecting said first capacitor in series with said resistance and said second capacitor across said bias source. I p e DIRK JOHAN BRAAK. REFERENCES CITED The following references are of record in' the file of this patent:

UNITED s r TEs PATENTS 9. In combination with a transceiver including a transmitter provided with a tuning circuit for Great Britain Feb. 24,1943 

